提交 b855d416 编写于 作者: P Patrick McHardy 提交者: Pablo Neira Ayuso

netfilter: nf_tables: fix nft_cmp_fast failure on big endian for size < 4

nft_cmp_fast is used for equality comparisions of size <= 4. For
comparisions of size < 4 byte a mask is calculated that is applied to
both the data from userspace (during initialization) and the register
value (during runtime). Both values are stored using (in effect) memcpy
to a memory area that is then interpreted as u32 by nft_cmp_fast.

This works fine on little endian since smaller types have the same base
address, however on big endian this is not true and the smaller types
are interpreted as a big number with trailing zero bytes.

The mask therefore must not include the lower bytes, but the higher bytes
on big endian. Add a helper function that does a cpu_to_le32 to switch
the bytes on big endian. Since we're dealing with a mask of just consequitive
bits, this works out fine.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
上级 ee214d54
...@@ -13,6 +13,16 @@ struct nft_cmp_fast_expr { ...@@ -13,6 +13,16 @@ struct nft_cmp_fast_expr {
u8 len; u8 len;
}; };
/* Calculate the mask for the nft_cmp_fast expression. On big endian the
* mask needs to include the *upper* bytes when interpreting that data as
* something smaller than the full u32, therefore a cpu_to_le32 is done.
*/
static inline u32 nft_cmp_fast_mask(unsigned int len)
{
return cpu_to_le32(~0U >> (FIELD_SIZEOF(struct nft_cmp_fast_expr,
data) * BITS_PER_BYTE - len));
}
extern const struct nft_expr_ops nft_cmp_fast_ops; extern const struct nft_expr_ops nft_cmp_fast_ops;
int nft_cmp_module_init(void); int nft_cmp_module_init(void);
......
...@@ -25,9 +25,8 @@ static void nft_cmp_fast_eval(const struct nft_expr *expr, ...@@ -25,9 +25,8 @@ static void nft_cmp_fast_eval(const struct nft_expr *expr,
struct nft_data data[NFT_REG_MAX + 1]) struct nft_data data[NFT_REG_MAX + 1])
{ {
const struct nft_cmp_fast_expr *priv = nft_expr_priv(expr); const struct nft_cmp_fast_expr *priv = nft_expr_priv(expr);
u32 mask; u32 mask = nft_cmp_fast_mask(priv->len);
mask = ~0U >> (sizeof(priv->data) * BITS_PER_BYTE - priv->len);
if ((data[priv->sreg].data[0] & mask) == priv->data) if ((data[priv->sreg].data[0] & mask) == priv->data)
return; return;
data[NFT_REG_VERDICT].verdict = NFT_BREAK; data[NFT_REG_VERDICT].verdict = NFT_BREAK;
......
...@@ -128,7 +128,7 @@ static int nft_cmp_fast_init(const struct nft_ctx *ctx, ...@@ -128,7 +128,7 @@ static int nft_cmp_fast_init(const struct nft_ctx *ctx,
BUG_ON(err < 0); BUG_ON(err < 0);
desc.len *= BITS_PER_BYTE; desc.len *= BITS_PER_BYTE;
mask = ~0U >> (sizeof(priv->data) * BITS_PER_BYTE - desc.len); mask = nft_cmp_fast_mask(desc.len);
priv->data = data.data[0] & mask; priv->data = data.data[0] & mask;
priv->len = desc.len; priv->len = desc.len;
return 0; return 0;
......
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